1. Field
The following description relates to an apparatus and method for tuning, for example, correcting a frequency.
2. Description of Related Art
A super regenerative receiver (SRR) is known as a low cost, easily configurable receiver having an appropriate reception sensitivity. SRRs have been widely applied to a variety of fields, such as the fields of remote control toys, information systems, and monitoring devices.
An SRR detects a signal based on a signal magnitude and a startup time of an oscillator in a circumstance in which an input signal is present. The signal magnitude and the startup time of the oscillator are based on a power and a frequency of a signal received at an antenna and a resonant frequency of the oscillator. When an input signal is absent, the SRR may oscillate very slowly due to thermal noise according to a magnitude of direct current (DC) bias set in the oscillator.
Since a super regenerative receiver (SRR) performs periodic quenching, a magnitude of bias current of an oscillator periodically varies during an operation of the SRR. Accordingly, an existing phase locked loop (PLL) scheme may not continuously control a frequency of the oscillator during the operation of the SRR.
Due to the above characteristic of the SRR, a method of calibrating a super regenerative oscillator (SRO) using a PLL before receiving data and turning off the PLL during the operation of the SRR may be employed. However, in the above method, leakage current occurs at a charge pump node during the operation of the SRR and, thus, a frequency of the SRO may drift.
A frequency control loop (FCL) is advantageous in a low power design compared to the existing PLL and a frequency drift may not occur during the operation of the SRR. However, a frequency offset may occur between an oscillation frequency of then SRO by the FCL in a calibration mode and an average resonant frequency of the SRR when receiving actual data. The frequency offset may degrade the performance of a bit error rate (BER) of the SRR.
Accordingly, there is a need for frequency synthesis technology for aligning an oscillation frequency of an SRO that is in low power and in a periodic quenching mode, and an actual frequency of data received via an antenna.